Redbelly98 said:
Saw this on Yahoo! News; the title pretty much sums it up.
http://news.yahoo.com/s/afp/20090105/ts_afp/usastronomy_090105234256
My question for the regular astro PFers: what would be the sun's revolution period around the galaxy based on this new information?
Redbelly, these results were under embargo until 5 Jan, yesterday. I searched yesterday and today for something more technical than the press-release material and couldn't find.
According to this report
http://www.guardian.co.uk/science/2009/jan/05/galaxy-collision-space-milky-way
the new estimate of the mass (including DM) is 270 billion solar mass. But this is similar to the estimates 200-400 billion that I have seen for some time!
So until I see some more technical report I don't know what to think. Maybe the real news is that they have narrowed down the uncertainty. And that the new more precise estimate is higher than yesterday's LOW estimates. However it turns out, we can address your question about the orbital period. The Harvard-Smithsonian press release is here
http://www.cfa.harvard.edu/press/2009/pr200903.html
and it implies the orbit radius is 28,000 LY, so assuming circular the circumf is 176,000 LY
and the estimated speed is 600,000 mph
So we just type into google something like
(176 000 lightyear) / (600 000 mph)
and google will say
(176 000 lightyear)/(600 000 mph) = 196 714 211 years
So we can quickly say the orbit period is 200 million years.
Indeed this is a tad shorter than what I remember from earlier. Back in 1970s I believe a common estimate was around 240 million years.
A good question would be if this 270 billion solar is right, then does that refer just to the mass inside the sun's orbit? Because their methodology seems to be good for finding the sun's orbital speed and that would just give a handle on what's inside our orbit. If they are trying to include an estimate of the outer part of the disc, then how are they doing that? Maybe someone else here will clarify.
